Fix a few crashes/hangs from general QS use

Just small general things whilst using QS

* if [objectDictionary allKeys] was nil then it'd cause a crash when trying to enumerate it
* The identifier could get released in ` + (void)registerObject:(QSBasicObject *)object withIdentifier:(NSString *)anIdentifier` if it was the same
* A hang on `loadAndReturnError` - I think it's an Apple bug (reported it to them) but checking to make sure the bundle is actually and `NSBundle` can't do any harm